Image reading apparatus with reference surface to generate reference data for shading correction, and related image forming apparatus and method

ABSTRACT

An image reading apparatus according to an embodiment includes an image reading unit configured to generate reference data by reading a reference surface and to generate image data by reading a sheet. A reference unit has a reference surface. A shading correction unit determines whether a portion of the reference surface includes a contaminant based on image data generated by the image reading unit reading the portion of the reference unit. When the portion of the reference surface is determined to not include a contaminant, the shading correction unit generates reference data based on the image data generated by the image reading unit reading the portion of the reference surface determined to not include a contaminant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/176,921, filed Oct. 31, 2018, which is a continuation of U.S. patentapplication Ser. No. 15/404,765, filed Jan. 12, 2017, now U.S. Pat. No.10,136,027, issued Nov. 20, 2018, the entire contents of each of whichare incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an image readingapparatus, an image forming apparatus, and a method for generating imagedata.

BACKGROUND

An image reading apparatus reads an image on a sheet by using an imagesensor such as a reduction optical system (a charge coupled device(CCD)) or a unit-magnification optical system (a contact image sensor(CIS)). The image reading apparatus may have individual variations inillumination from a light source for illuminating a reading surface of asheet or vignetting from a lens of the image sensor. The differencesoccur during manufacture and also occur due to aging degradation of theapparatus. The individual variations are a factor for generatingirregularities in image data by reading. Therefore, a shading correctionfor correcting the irregularities in the image is performed.

The shading correction requires white reference data indicating areference value of brightness corresponding to white. The whitereference data is generated by reading a white reference surface whichis provided on the image reading apparatus. Therefore, if a contaminantis on the reference plate surface, suitable white reference data is notacquired and there is a possibility that accuracy in the shadingcorrection is lowered.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective diagram illustrating an example configuration ofan image forming apparatus according to an embodiment.

FIG. 2 illustrates an example schematic configuration of the imageforming apparatus.

FIG. 3 illustrates an example internal configuration of a first imagereading unit.

FIG. 4 illustrates an example configuration of a second reading unit.

FIG. 5 is a flowchart illustrating an example sequence of operationswhen power is turned on in the image forming apparatus.

FIG. 6 is a flowchart illustrating an example sequence of operations forreading a sheet.

FIG. 7 is a flowchart illustrating a second example sequence ofoperations for reading the sheet.

DETAILED DESCRIPTION

An image reading apparatus according to an embodiment includes an imagereading unit configured to generate reference data by reading areference surface and to generate image data by reading a sheet. Areference unit has a reference surface. A shading correction unitdetermines whether a portion of the reference surface includes acontaminant based on image data generated by the image reading unitreading the portion of the reference unit. When the portion of thereference surface is determined to not include a contaminant, theshading correction unit generates reference data based on the image datagenerated by the image reading unit reading the portion of the referencesurface determined to not include a contaminant.

Hereinafter, an image reading apparatus, an image reading method, and animage forming apparatus, of the embodiment will be described withreference to drawings.

FIG. 1 is a perspective diagram illustrating an example configuration ofan image forming apparatus 100 according to an embodiment. The imageforming apparatus 100 is, for example, a multifunction peripheral. Theimage forming apparatus 100 includes a display 110, a control panel 120,a printer unit 130, a sheet housing unit 140, and an image reading unit200. The printer unit 130 of the image forming apparatus 100 may be adevice which forms a toner image, or may be an ink jet type device.

The image forming apparatus 100 forms an image on a sheet using adeveloper such as toner. The sheet is, for example, a paper, or a labelsheet. The sheet may be any sheet as long as an image can be formed onthe front surface of the sheet by the image forming apparatus 100.

The display 110 is an image display device such as a liquid crystaldisplay (LCD), or an organic electro luminescence (EL) display. Thedisplay 110 displays various types of information items relating to theimage forming apparatus 100.

The control panel 120 includes a plurality of buttons. The control panel120 receives input of an operation from a user. The control panel 120outputs a signal in accordance with the operation input by the user to acontrol unit of the image forming apparatus 100. The display 110 and thecontrol panel 120 may be configured as an integrated touch panel.

The printer unit 130 forms an image on the sheet based on imageinformation generated by the image reading unit 200 or image informations received through a communication interface. The printer unit 130 formsan image by the following process, for example. An image forming unit ofthe printer unit 130 forms an electrostatic latent image on aphotoreceptor drum based on the image information. The image formingunit of the printer unit 130 forms a visible image by applying adeveloper to the electrostatic latent image. As an example of thedeveloper, toner may be used. A transfer unit of the printer unit 130transfers the visible image to a sheet (different from a target sheetthat was read). The fixing unit of the printer unit 130 fixes thevisible image on the sheet by performing heating and pressing the sheet.The sheet on which the image is formed may be a sheet which is stored inthe sheet housing unit 140. Alternatively, the sheet may be manuallyfed.

The sheet housing unit 140 stores the sheet to be used for forming animage in the printer unit 130.

The image reading unit 200 reads image information of a read target asbrightness and darkness of light. The image reading unit 200 records theread image information. The recorded image information may betransmitted to the other information processing device through anetwork. The recorded image information may be formed on the sheet bythe printer unit 130.

FIG. 2 illustrates an example schematic configuration of the imageforming apparatus 100.

The image forming apparatus 100 includes a central processing unit (CPU)10, a memory 20, and an auxiliary storage device 30 which is connectedby a bus and executes a program. The image forming apparatus 100includes the display 110, the control panel 120, the printer unit 130,the sheet housing unit 140, and the image reading unit 200, controlledby executing the program. The various functions or a part of the imageforming apparatus 100 may be implemented using the hardware such as anapplication specific integrated circuit (ASIC), a programmable logicdevice (PLD), or a field programmable gate array (FPGA). The program maybe recorded on a computer readable recording medium. The computerreadable recording medium is, for example, a portable medium such as aflexible disk, a magnetic disk, a ROM, and a CD-ROM, and a storagedevice such as a hard disk equipped in a computer system. The programmay be transmitted over a network connection.

The CPU 10 reads the program stored in the auxiliary storage device 30into the memory 20 and executes the program. Thereby, the CPU 10 servesas a control unit for controlling each functional unit of the imageforming apparatus 100. The CPU which serves as the control unit may beprovided individually in each functional unit.

The memory 20 is, for example, a random access memory (RAM). The memory20 stores data to be used by each functional unit which is included inthe image forming apparatus 100, temporarily. The memory 20 may storedigital data generated by the image reading unit 200.

The auxiliary storage device 30 is, for example, a hard disk or a solidstate drive (SSD) and stores various types of data items. The varioustypes of data items are, for example, image data. The image data isdigital data generated by the image reading unit 200.

The image reading unit 200 further includes a shading correction unit 70and a control unit 80.

The shading correction unit 70 generates reference data used for theshading correction based on the image data generated by imaging thereference surface when the light source is turned on or imaging when thelight source is turned off. The reference data is data indicating acolor which serves as a reference for the shading correction. Theshading correction unit 70 performs the shading correction with respectto the image data generated by reading of the sheet, based on thegenerated reference data. In addition, the shading correction unit 70generates data which serves as a reference when detecting whethercontaminant is on the reference surface, based on the image data(hereinafter, referred to as “reference data for detecting acontaminant”) obtained by imaging the reference surface. The shadingcorrection unit 70 may be implemented using the hardware such as anASIC, a PLD, or a FPGA.

The control unit 80 controls operations of each of functional unitsincluded in the image forming apparatus 100. The function of the shadingcorrection unit 70 may be implemented by the control unit 80. That is,the shading correction unit 70 and the control unit 80 may be integrallyconfigured, or may be configured separately.

FIG. 3 illustrates an example configuration of an image reading unit200.

The image reading unit 200 includes an automatic document feeder (ADF)40 and a first reading unit 50. Here, the ADF 40 functions as a readingdevice of a sheet back surface and the first reading unit 50 functionsas a reading device of a sheet front surface.

The ADF 40 includes a sheet placement unit 41, a sheet feeding roller411, a separation roller 412, a registration roller 413, a transportingroller 414 a, a transporting roller 414 b, a transporting roller 414 c,a transporting roller 414 d, a sheet discharging roller 415, a sheetdischarging unit 42, and a second reading unit 43.

A sheet is initially positioned on the sheet placement unit 41.

The sheet feeding roller 411 feeds the sheet positioned on the sheetplacement unit 41.

The separation roller 412 separates the sheets fed by the sheet feedingroller 411 one by one and feeds the sheet to registration roller 413.

The registration roller 413 aligns a leading end of the sheet fed fromthe separation roller 412. The registration roller 413 sends the sheetin which the leading end is aligned in a sheet transport direction.

The transporting rollers 414 a, 414 b, 414 c, and 414 d send the sheettransported by the registration roller 413 in the sheet transportdirection. In the following description, when the transporting rollers414 a, 414 b, 414 c, and 414 d are not distinguished from each other,the rollers are collectively referred to as the transporting rollers414.

The sheet discharging roller 415 sends the sheet transported by thetransporting roller 414 to the sheet discharging unit.

The sheet discharging unit 42 stacks the sheet sent by the transportingroller 414.

The second reading unit 43 includes a light source lighting the backsurface of the sheet and an image sensor such as a CCD or CIS. Thesecond reading unit 43 generates image data of the back surface bylighting the back surface of the transported sheet with the light sourceand reading the back surface.

Furthermore, the ADF 40 includes various types of sensors for detectingthe sheet moving on a transporting path. Specifically, the ADF 40further includes a post-separation sensor 421, a registration sensor422, a front surface position sensor 423, a rear surface position sensor424, and a sheet discharging sensor 425.

The post-separation sensor 421 detects the sheet sent from theseparation roller 412.

The registration sensor 422 detects the sheet which is transported tothe registration roller 413.

The front surface position sensor 423 detects the sheet sent toward areading position (hereinafter, referred to as a “front surface readingposition”) of the first reading unit 50 from the transporting roller 414b.

The back surface position sensor 424 detects the sheet sent toward areading position (hereinafter, referred to as a “back surface readingposition”) of the second reading unit 43 from the transporting roller414 c.

The sheet discharging sensor 425 detects the sheet sent from the sheetdischarging roller 415 toward the sheet discharging unit 42.

The first reading unit 50 includes a light source lighting the frontsurface of the sheet displaced on the sheet placement unit 41 and animage sensor such as a CCD or CIS. The first reading unit 50 generatesimage data of the front surface by lighting the front surface of thesheet displaced on the sheet placement unit 41 with the light source andreading the back surface.

FIG. 4 illustrates an example configuration of the second reading unit43.

The second reading unit 43 includes a reference roller 431 and a scannermodule 432.

When the reading of the sheet back surface is performed, the referenceroller 431 plays a role of a guide for the sheet and also includes areference surface (first surface) for acquiring the reference data to beused to perform the shading correction. Among the roller surfaces of thereference roller 431, an area other than the reference surface isreferred to as a standby surface (second surface). For example, asillustrated in FIG. 4, the reference roller 431 includes each half ofthe roller surface as the reference surface and the standby surface.

The reference roller 431 can be rotated with respect to the papersurface by controlling the driving unit (for example, a motor or thelike) by the control unit 80. By rotating, the reference roller 431 canchange the positions of the reference surface and the standby surfacewith respect to the scanner module 432. When the reference data isacquired, the control unit 80 rotates the reference roller 431 so thatthe scanner module 432 faces the reference surface. On the other hand,when the reference data is not acquired, the control unit 80 rotates thereference roller 431 so that the scanner module 432 faces the standbysurface. By controlling the reference roller 431 in this manner, theimage forming apparatus 100 can prevent a contaminant from adhering tothe reference surface due to contact with the sheet or the like.

In addition, the reference roller 431 includes a background surface thatserves as a background of the read sheet. For example, as illustrated inFIG. 4, the reference roller 431 includes the background surface whichoccupies the half of the standby surface. The background surface has abackground color (for example, black) which is distinguishable from theoutline of the sheet.

The scanner module 432 includes a light source for lighting the sheet tobe read and an image sensor such as a CCD or CIS. The scanner module 432generates image data of the sheet back surface by reading the backsurface of the transported sheet. In addition, the scanner module 432generates the reference data by imaging the reference surface with thelighting source turned on or imaging when the lighting source is turnedoff.

When the reading of the non-standard sized sheet is performed, thecontrol unit 80 controls the reference roller 431 so that the backgroundsurface is positioned at the reading position of the scanner module 432.On the other hand, when the reading of the standard sized sheet isperformed, the control unit 80 controls the reference roller 431 so thatthe portion other than the background surface among the standby surfaceis positioned at the reading position of the scanner module 432.

The description returns FIG. 3. The first reading unit 50 includes alight source for lighting a front surface of the sheet placed on thesheet placement unit 41 and an image sensor such as the CCD or the CIS.The first reading unit 50 generates image data of the front surface bylighting the front surface of the sheet placed on the sheet placementunit 41 with the light source and reading the front surface.

The image forming apparatus 100 of the embodiment generates or updatesthe reference data for detecting a contaminant using at least thefollowing timings under the control of the control unit 80, to therebyperform the shading correction with higher accuracy:

(1) When power is turned on; and

(2) When image data is generated by reading a sheet.

Hereinafter, an operation example of the image forming apparatus 100 atthe above timing will be described.

FIG. 5 is a flowchart illustrating an example sequence of operationswhen turning on the power in the image forming apparatus 100.

First, the control unit 80 moves the reference surface by rotating thereference roller 431 (ACT 101). Specifically, the control unit 80 movesthe reference surface to a predetermined reference position(hereinafter, referred to as a “first reference position”) with respectto the scanner module 432.

The first reference position is a position where the scanner module 432starts reading the reference surface. The scanner module 432 startsreading the reference surface in a state where the reference surface ispositioned at the first reference position. The scanner module 432 canimage the entire the reference surfaces by continuously imaging thereference surface which is rotated a predetermined amount in onedirection. For example, the control unit 80 rotates the reference roller431 so that an edge of the reference surface becomes an edge of thereading range of the scanner module 432 in the transporting direction asa first reference position. The information indicating a rotating amountof the reference surface by the predetermined amount may be stored inadvance in an internal storage of the image reading unit 200 or the ADF40.

Subsequently, the control unit 80 executes a gain adjustment processthat is a pre-process for acquiring image data (ACT 102). The gainadjustment process is a process of determining the gain for maintainingstrength of an output signal with respect to strength of an input signalat a certain level. Specifically, the control unit 80 reads thereference surface which is positioned on the first reference position bycontrolling the scanner module 432 and detects a peak of a brightnessdistribution for the image data of the acquired reference surface. Thecontrol unit 80 determines the gain for correcting the brightness inaccordance with a target output strength based on the detected peakbrightness (hereinafter, referred to as a “peak brightness”).Thereafter, the determined gain is used for correcting the image whichis imaged by the scanner module 432.

As described above, the reference surface is read to obtain a whitelevel reference value that is applied to the brightness value.Therefore, by executing the gain adjustment process of ACT 102, thewhite level of the image data is adjusted.

Subsequently, the shading correction unit 70 generates the referencedata for detecting a contaminant based on the image data of thereference surface output from the scanner module 432 (ACT 103).Specifically, the reference data for detecting a contaminant isgenerated as information indicating a threshold value of the brightnessvalue which can distinguish between an area with a contaminant adheredthereto and an area with no contaminant. For example, the shadingcorrection unit 70 generates information indicating a maximum brightnessvalue in the image of the reference surface which is imaged whilerotating the reference roller 431 at a predetermined amount as thereference data for detecting a contaminant. The reference data fordetecting a contaminant is not necessarily information indicating themaximum value of the brightness value. For example, the reference datafor detecting a contaminant be information indicating any value as longas the information can be used as the threshold value of the brightnessvalue which can distinguish between an area with a contaminant and anarea with no contaminant. For example, the reference data for detectinga contaminant may be information indicating a minimum value, an averagevalue, and an intermediate value, of the brightness values of areasassumed to have a contaminant. The shading correction unit 70 maintainsthe reference data for detecting a contaminant generated in such thatmanner in the internal storage region.

Subsequently, the control unit 80 determines whether the shadingposition is previously determined in own apparatus (ACT 104). Theshading position is a position on the reference surface at which thewhite reference data is acquired. The shading position is specifiedaccording to the state where the contaminant is on the reference surfaceand is indicated by shading information (positional information). If theapparatus already stores the shading information, the control unit 80determines that the shading position is previously determined, and ifthe apparatus does not already store the shading information, thecontrol unit 80 determines that the shading position is not determined.

When the shading position is previously determined (ACT 104: YES), thecontrol unit 80 ends the process without performing a process fordetermining the shading position. On the other hand, when the shadingposition is not determined (ACT 104: NO), the shading correction unit 70executes a contaminant detection process with respect to the referencesurface within the imaging range using the reference data for detectinga contaminant generated in ACT 103 (ACT 105). The contaminant detectionprocess is a process for detecting the contaminant on the referencesurface by comparing the reference data for detecting a contaminant andeach brightness value of the image data in which the reference surfaceis imaged. By rotating the reference roller 431 at a predeterminedamount, the control unit 80 controls the reference roller 431 and theshading correction unit 70 such that the contaminant detection processis executed for the entire reference surface.

The determination of whether the reference surface has a contaminant maybe determined by an arbitrary method depending on the specific referencedata for detecting a contaminant. For example, when the reference datafor detecting a contaminant includes a brightness value indicating themost severe contaminant (that is, the maximum value in the image data),the shading correction unit 70 may detect a region of the referencesurface corresponding to a pixel having a brightness value closest tothe reference data for detecting a contaminant as a region with thecontaminant. In addition, for example, when the reference data fordetecting a contaminant includes the brightness value indicating themost mild contaminant (that is, the minimum value within a range inwhich the contaminant is assumed to adhere), the shading correction unit70 may detect the region of the reference surface corresponding to thepixel having the brightness value higher than that of the reference datafor detecting a contaminant as a region with the contaminant.

The control unit 80 determines whether the contaminant on the referencesurface is detected in the contaminant detection process (ACT 106). Whenthe contaminant on the reference surface is detected in the contaminantdetection process (ACT 106: YES), the control unit 80 rotates thereference roller 431 a predetermined rotation amount (ACT 107). Byrotating of the reference roller 431, a new region of the referenceroller 431 becomes the imaging target of the scanner module 432. Thecontrol unit 80 stores the number of the rotations of the referenceroller 431 (hereinafter, the “number of accumulated rotations”) andupdates the number of the accumulated rotations according to theexecution of ACT 107.

Subsequently, the control unit 80 determines whether the number of theaccumulated rotations of the reference roller 431 has reached thepredetermined maximum number of the rotations (ACT 108). The maximumnumber of the rotations is determined in advance based on one fullrotation of the reference roller 431 and the size of the referencesurface. By performing the rotation of the reference roller 431 at themaximum number, the contaminant detection process is executed on theentire reference surface.

When the accumulated number of the rotations of the reference roller 431is not the maximum number (ACT 108: NO), the control unit 80 returns tothe process in ACT 105, and the contaminant detection process isexecuted with respect to the region of the reference surface which is tobe a new imaging target with respect to the shading correction unit 70.

On the other hand, when the accumulated number of the rotations of thereference roller 431 has reached the maximum value (ACT 108: YES), thecontrol unit 80 rotates the reference roller 431 (ACT 109) so that thereference surface is returned to a predetermined reference position. Thereference position here may be any position where the scanner module 432can perform the reading of the reference surface. For example, thereference position may be the first reference position. The informationindicating the predetermined reference position may be stored in aninternal storage region of the image reading unit 200 or the imageforming apparatus 100 in advance. Here, by returning the referencesurface to the predetermined reference position, it is possible to avoida status in which the image reading unit 200 is locked and is notoperable. The locked state of the image reading unit 200 is a state inwhich the shading position cannot be determined. If the shading positioncannot be determined, the shading correction unit 70 cannot perform theshading correction, and the scanning cannot be finished.

Subsequently, the control unit 80 notifies a user that the shadingposition cannot be determined (ACT 110). For example, the notificationis provided to the user or a maintenance person of the image formingapparatus 100. In this time, the control unit 80 may store theinformation indicating that the shading position cannot be determined inan internal storage region. In this manner, when the maintenance of theimage forming apparatus 100 is performed, the notification that thereference surface is contaminated is acknowledged by the maintenanceperson.

In addition, on the other hand, when the contaminant on the referencesurface cannot be detected in the contaminant detection process in ACT105 (ACT 106: NO), the control unit 80 determines the position of thereference surface at the time point thereof as the shading position (ACT111). The control unit 80 generates and stores the shading informationindicating the position of the reference surface which is determined asthe shading position. If the control unit 80 generates the shadinginformation, the control unit 80 retracts the reference surface byrotating the reference roller 431 so that the standby surface faces thescanner module 432 (ACT 112). After the retraction of the referencesurface is finished, the control unit 80 ends the process.

FIG. 6 is a flowchart illustrating a first example sequence ofoperations for reading the sheet in the image forming apparatus 100.

FIG. 6 indicates an example of a process to be executed before startingthe job according to the generation of the job in the image formingapparatus 100. The job here means a series of operations associated withthe reading of the sheet by the image reading unit 200. Specifically,the job is generated in response on instructions for performing aprocess such as a copy process for copying the image formed on the sheetto the other sheet or a scan process for generating image data forreading the image which is formed on the sheet.

First, when the job is generated in the image forming apparatus 100, thecontrol unit 80 reads the shading information stored in the apparatus(ACT 201). The control unit 80 rotates the reference roller 431, andmoves the reference surface to the shading position indicated by theread shading information (ACT 202).

When the reference surface is moved to the shading position, the controlunit 80 turns off the light source and controls the acquisition of theblack reference data using the second reading unit 43 and the shadingcorrection unit 70. At this time, the second reading unit 43 performs animaging operation in a state with the light source is turned off, andoutputs the generated image data to the shading correction unit 70. Theshading correction unit 70 generates the black reference data based onthe image data which is acquired in the state where the light source isturned off (ACT 203).

Subsequently, the control unit 80 turns on the light source and controlsthe acquisition of the white reference data using the second readingunit 43 and the shading correction unit 70. At this time, the secondreading unit 43 performs an imaging operation in a state with the lightsource is turned on, and outputs the generated image data of theilluminated reference surface to the shading correction unit 70. Theshading correction unit 70 generates the white reference data based onthe image data of the illuminated reference surface (ACT 204).

When the acquisition of the reference data is finished, the control unit80 determines whether the size of the sheet to be read is a name cardsize (ACT 205). For example, if the user designates the size of thesheet to be read, the control unit 80 can distinguish the sheet sizebased on the input information of the user. In addition, the imageforming apparatus 100 may include a unit for transporting the sheetwhich is transported to the first reading unit 50 and the second readingunit 43 to a previous stage of the first reading unit 50 again. In sucha case, the control unit 80 may detect the sheet size with the firstreading unit 50 or the second reading unit 43.

When the size of the sheet to be read is not the name card size (ACT205: NO), the control unit 80 retracts the reference surface by rotatingthe reference roller 431 so that the standby surface faces the scannermodule 432 (ACT 206), and ends the process. On the other hand, when thesize of the sheet to be read is the name card size (ACT 205: YES), thecontrol unit 80 moves the reference surface to the second referenceposition (ACT 207), and ends the process.

The second reference position is a position of the reference surface ina state where the scanner module 432 faces the second standby surface.That is, the sheet having the name card size is read in a state wherethe reference surface is positioned on the second reference position, sothat the generated image data includes the second standby surface asbackground. As described above, since the second standby surface isblack, the edge between the sheet and the background can be emphasized,and it is possible to more correctly detect the deviation of thedirection of the sheet. In this manner, by generating the image data inwhich the second standby surface is set as the background with respectto the sheet having the name card size where the skew is easilygenerated, the image forming apparatus 100 of the embodiment can morecorrectly correct the skew of the image data.

When the reference surface is moved to the position in accordance withthe sheet size, the control unit 80 transports the sheet to be read tothe second reading unit 43 and executes the reading of the sheet withrespect to the second reading unit 43 (ACT 208).

FIG. 7 is a flowchart illustrating a second example sequence ofoperations for reading of the sheet in the image forming apparatus 100.

FIG. 7 illustrates an example of a process to be executed after theimage generation is ended in the image forming apparatus 100 of theembodiment.

First, when the execution of the job is finished in the image formingapparatus 100, the control unit 80 reads the stored shading information(ACT 301). By rotating the reference roller 431, the control unit 80moves the reference surface to the shading position indicated by theread shading information (ACT 302).

When the reference surface is moved to the shading position, the shadingcorrection unit 70 executes a contaminant detection process with respectto the reference surface within the imaging range, using the previouslystored reference data for detecting a contaminant (ACT 303). Thecontaminant detection process to be executed here is the same process asthe contaminant detection process illustrated in FIG. 4.

The control unit 80 determines whether a contaminant on the referencesurface is detected in the contaminant detection process (ACT 304). Whena contaminant on the reference surface is detected in the contaminantdetection process (ACT 304: YES), the control unit 80 rotates thereference roller 431 at a predetermined rotation amount (ACT 305).

Subsequently, the control unit 80 determines whether the number of theaccumulated rotations of the reference roller 431 is reached thepredetermined maximum number of rotations (ACT 306). When theaccumulated number of the rotations of the reference roller 431 has notreached the maximum number (ACT 306: NO), the control unit 80 returns tothe process in ACT 303, and the contaminant detection process isexecuted with respect to the region of the reference surface which is tobe a new imaging target with respect to the shading correction unit 70.

On the other hand, when the accumulated number of the rotations of thereference roller 431 is reached the maximum value (ACT 306: YES), thecontrol unit 80 rotates the reference roller 431 (ACT 307), until thereference surface is returned to a predetermined reference position. Thereference position here may be any position as long as the referenceposition is a position where the scanner module 432 can perform thereading of the reference surface. For example, the reference positionmay be the first reference position. The information indicating thepredetermined reference position may be stored in an internal storageregion of the image reading unit 200 or the image forming apparatus 100in advance. By returning the reference surface to the predeterminedreference position, it is possible to avoid a status in which the imagereading unit 200 is locked and not operable.

Subsequently, the control unit 80 notifies a user that the shadingposition cannot be determined (ACT 308). For example, the notificationis provided to the user or a maintenance person of the image formingapparatus 100. At this time, the control unit 80 may store theinformation indicating that the shading position cannot be determined inan internal storage region. Accordingly, when the maintenance of theimage forming apparatus 100 is performed, the notification that thereference surface is contaminated can be provided to the maintenanceperson.

In addition, on the other hand, when no contaminant on the referencesurface is detected in the contaminant detection process in ACT 303 (ACT304: NO), the control unit 80 determines the current position of thereference surface as the new shading position (ACT 309). The controlunit 80 generates the shading information indicating the position of thereference surface which is determined as the new shading position andupdates the original shading information with new shading information.If the control unit 80 generates the new shading information, thecontrol unit 80 retracts the reference surface by rotating the referenceroller 431 so that the standby surface faces the scanner module 432 (ACT310). After the retraction of the reference surface is finished, thecontrol unit 80 ends the process.

The image forming apparatus 100 includes the control unit 80 fordetecting the contaminant adhering to the reference surface andgenerating the white reference data which is required for the shadingcorrection. The control unit 80 generates the white reference data usingthe image data from the region where the contaminant cannot be detectedin the reference surface. Therefore, even if the contaminant is on apart of the reference surface, the appropriate white reference data canbe generated by avoiding the region, and the shading correction can beimplemented with higher accuracy.

Hereinafter, modification examples of the image reading apparatus, theimage reading method, and the image forming apparatus of embodiment willbe described.

The image reading unit 200 which is provided on the image formingapparatus 100 of the above-described embodiment may be provided as animage reading apparatus which is independent from the image formingapparatus 100.

The image forming apparatus 100 of the above-described embodiment mayfurther include a heating unit for decoloring an image formed using adecolorable toner by heating the sheet. In this case, the heating unitmay be a fixing unit of the printer unit 130.

A name card size of the above-described embodiment is an example of asheet size (non-standard size) smaller than the standard size. Thenon-standard size may be any sheet size other than the name card size aslong as the sheet size is smaller than the standard size.

In this embodiment, “decoloring” means to make it difficult to recognizea color of an image formed on an image receiving member after the imageis formed on the image receiving member by a recording material whichhas different color from the color of the image receiving material. Thecolor of recording material may be any color including black, white, ora chromatic color.

While certain embodiments have been described these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms: furthermore variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention.

What is claimed is:
 1. An image reading apparatus comprising: a scannerconfigured to emit light and generate image data based on reflectedlight; and a reference roller configured to rotate around a rotationaxis and by which the emitted light is reflected, wherein the referenceroller includes a first flat planar surface which extends in a firstdirection parallel to the rotation axis and in a second directionperpendicular to the first direction, and an arcuate surface whichextends parallel to the rotation axis.
 2. The apparatus of claim 1,wherein the first flat planar surface and a center of the arcuatesurface face opposite directions.
 3. The apparatus of claim 1, whereinthe first flat planar surface and the arcuate surface are notcontinuously connected to each other.
 4. The apparatus of claim 1,wherein the reference roller includes a second flat planar surfaceextending in the first direction and a third direction that isperpendicular to the first and second directions, and connected to thefirst flat planar surface.
 5. The apparatus of claim 4, wherein thereference roller includes a third flat planar surface connected to thefirst flat planar surface and parallel to the second flat planarsurface.
 6. The apparatus of claim 5, wherein the reference rollerincludes a fourth flat planar surface connected to the second flatplanar surface and one side of the arcuate surface extending parallel tothe axis, and a fifth flat planar surface connected to the third flatplanar surface and another side of the arcuate surface opposite to saidone side of the arcuate surface.
 7. The apparatus of claim 1, wherein alength of one side of the first flat planar surface in the seconddirection is shorter than a length of a chord of an arcuate side of thearcuate surface.
 8. The apparatus of claim 1, wherein the first flatplanar surface is a reference surface that faces the scanner for thescanner to generate reference data for shading correction.
 9. Theapparatus of claim 1, wherein the arcuate surface includes a backgroundsurface that faces the scanner to scan a medium.
 10. The apparatus ofclaim 9, wherein the first flat planar surface is a reference surfacethat faces the scanner for the scanner to generate reference data forshading correction, and the arcuate surface includes a standby surfacethat faces the scanner after the reference data has been generated. 11.An image forming apparatus comprising: a scanner configured to emitlight and generate image data based on reflected light; a referenceroller configured to rotate around a rotation axis and by which theemitted light is reflected; and a printer configured to print on a sheetbased on the generated image data, wherein the reference roller includesa first flat planar surface which extends in a first direction parallelto the rotation axis and in a second direction perpendicular to thefirst direction, and an arcuate surface, which extends parallel to therotation axis.
 12. The apparatus of claim 11, wherein the first flatplanar surface and a center of the arcuate surface face oppositedirections.
 13. The apparatus of claim 11, wherein the first flat planarsurface and the arcuate surface are not continuously connected to eachother.
 14. The apparatus of claim 11, wherein the reference rollerincludes a second flat planar surface extending in the first directionand a third direction that is perpendicular to the first and seconddirections, and connected to the first flat planar surface.
 15. Theapparatus of claim 14, wherein the reference roller includes a thirdflat planar surface connected to the first flat planar surface andparallel to the second flat planar surface.
 16. The apparatus of claim15, wherein the reference roller includes a fourth flat planar surfaceconnected to the second flat planar surface and one side of the arcuatesurface extending parallel to the axis, and a fifth flat planar surfaceconnected to the third flat planar surface and another side of thearcuate surface opposite to said one side of the arcuate surface. 17.The apparatus of claim 11, wherein a length of one side of the firstflat planar surface in the second direction is shorter than a length ofa chord of an arcuate side of the arcuate surface.
 18. The apparatus ofclaim 11, wherein the first flat planar surface is a reference surfacethat faces the scanner for the scanner to generate reference data forshading correction.
 19. The apparatus of claim 11, wherein the arcuatesurface includes a background surface that faces the scanner to scan amedium.
 20. The apparatus of claim 19, wherein the first flat planarsurface is a reference surface that faces the scanner for the scanner togenerate reference data for shading correction, and the arcuate surfaceincludes a standby surface that faces the scanner after the referencedata has been generated.